History of subwy.
Rapid transit evolved from steam railways during the late 19th century. In 1890 the City & South London Railway in London was the first electric rapid transit railway. The electric railway eventually was merged into London Underground. The technology swiftly spread to other cities in Europe, as in Budapest, Hungary in 1896, and then to the United States. A number of elevated systems were built, starting with the 1893 100% designed electric Liverpool Overhead Railway, which also had a small underground section complete with station. The elevated railways in Chicago and New York were converted to electric from steam propulsion.
By 1940, there were 19 systems, and by 1984, there were 66. This included smaller cities like Oslo and Marseille which opened extensive systems in the 1960s. More recently the growth of new systems has been concentrated in Southeast Asia and Latin America. Western Europe and North America have instead seen a revival of the tram, with light rail systems supplementing full scale urban railways, and less focus on building rapid transit. At the same time, technological improvements have allowed new driverless lines and systems. Hybrid solutions have also evolved, such as tram-train and premetro, which have some of the features of rapid transit systems.
Since the 1980s trams have incorporated several features of rapid transit: light rail systems (trams) run on their own rights-of-way, thus avoiding congestion; they remain on the same level as buses and cars. Some light rail systems have elevated or underground sections. Both new and upgraded tram systems allow faster speed and higher capacity, and are a cheap alternative to construction of rapid transit, especially in smaller cities.
Premetro means that an underground rapid transit is built in the city center, but only a light rail or tram system in the suburbs. Conversely, other cities have opted to build a full metro in the suburbs, but run trams in city streets to save the cost of expensive tunnels. In North America, interurbans were constructed as street-running suburban trams, without the grade-separation of rapid transit. Premetros also allow a gradual upgrade of existing tramways to rapid transit, thus spreading the investment costs over time. They are most common in Germany with the name Stadtbahn.
Suburban Commuter rail is a heavy rail system that operates at a lower frequency than urban rapid transit, with higher average speeds, often only serving one station in each village and town. Commuter rails of some cities (such as German S-Bahns, Merseyrail, Chennai rail, Australia cityrails (Transperth, Metro Trains Melbourne, Queensland Rail (Brisbane), CityRail (Sydney)), Danish S-tog etc. widely provide a mass transit within city as urban metro systems. As opposition, in some cities (such as PATH in New York, Dubai Metro, Mecca Metro, Los Teques Metro, Tyne & Wear Metro, some of other Brazilian metros, MetroSur and other lines of Madrid Metro, Singapore MRT, Taipei Metro, Kuala Lumpur's RapidKL Light Rail Transit etc.) the mainly urban rapid transit systems branch out to the nearest suburbs. Some cities have opted for a hybrid solution, with two tiers of rapid transit: an urban system (such as the Paris Métro, Berlin U-Bahn, London Underground) and a suburban system with lower frequency (such as their counterparts RER, S-Bahn, future Crossrail, respectively). The suburban systems run on their own tracks with high frequency, but are often quite similar to commuter rail, and are often operated by the national railways. In some cities the national railway runs through tunnels in the city center; sometimes commuter trains have direct transfer to the rapid transits, on the same or adjoining platforms. California's BART system functions as a hybrid of the two: in the suburbs, it functions like a commuter rail, with longer trains, longer intervals, and longer distance between stations; in downtown San Francisco, many lines join and intervals drop to normal subway levels, and stations become closer together. Also, some other urban or "near urban" rapid transit systems (GuangFo Metro Line 1, East Rail Line in Hong Kong, Guarenas-Guatire etro, Mumbai-Thane rail, Chennai MRTS (not to be confused with Chennai rail), Bundang Line, Sin Bundang Line, Jungang Line, Gyeongui Line, and Gyeongchun Line in the Seoul Metropolitan Area, Euskotren Trena in the Basque County etc.) serves the bi- and multi- nucleous agglomerations.